What are maintenance and reliability?

Maintenance and reliability are important assets of operations management. It is keeping the equipment and system in proper working condition. Reliability is the term used for denoting the probability that the machine or system will work properly. The concepts of maintenance and reliability are widely used by the operations manager for proper logistics and supply chain management. They also play an important role in the practices that lead to more productivity of a system at less cost.

Maintenance

Maintenance is keeping the equipment and system in proper working condition. It plays an important role in deciding the cost of any project being undertaken by the company. It has high importance in most industries because the machines and equipment in the industries need frequent maintenance, and hence, separate costs need to be incurred for the maintenance of the objects. It is the qualitative and quantitative measure of any system, which deals with its design and installation. The maintenance allows a system to achieve the desired objective with minimum expenditure. Any system is designed in such a way that the geometric mean of all the active repair time intervals required to repair the independent failures must not exceed the equipment repair time.

The various elements of maintenance

Design decisions

For a proper and good maintenance, the design of any system should be modular. The fasteners used in the machinery should be as per the standards and of limited variety and sizes. The components of the machinery should be interchangeable. The machinery should be designed in such a way that the parts can be opened easily and faults can be detected correctly. The components used should be chosen with fail-safe measures. To avoid any problem due to a wrong connection, better techniques, preferably color coding should be done.

Maintenance policies

The maintenance policies should be made clear during the designing phase of a material. The decision of discarding or repairing any equipment shall be done as per the conditions like the economy, the time required, the lifespan of equipment, and so on. The system should be properly monitored and proper instruments should be designed for the same. Use of torque wrenches and many other efficient tools should be done for efficient maintenance. The use of cranes and some other lifting mechanisms should be done to increase efficiency and reduce time.

Technician requirement

The technicians used for maintenance purposes should be well educated, trained, and experienced. Preferably, a maintenance engineer should be hired for this role. Proper training should be given to the maintenance technician so that the technician can properly analyze and understand the procedures.

The maintenance strategy usually used is simple and depends only on two factors, employee involvement, and maintenance procedures. Employee involvement includes proper and relevant information sharing with the employees, giving skill training to the employees, and rewarding the employees for employee empowerment. The result of using a proper maintenance strategy is reduced inventory, improved quality and capacity, an improved reputation of quality, continuous improvement, and reduced variability.

Types of maintenance

There are two types of maintenance - preventive maintenance and breakdown maintenance.

• Preventive maintenance is the routine inspection and servicing of the facilities to keep them in good and working condition. The main motive of preventive maintenance is to avoid any kind of damage to the equipment and, to reduce the repairing cost.
• Breakdown maintenance is the emergency or priority repairs on the failed equipment. The breakdown maintenance is done on the damaged or failed equipment.

Reliability

Reliability is the probability that the machine or system will work properly. Following are the four aspects of reliability-

• It means that the design and development of the product should be such that it meets or exceeds the specified requirements.
• It is a probability-based concept with a value ranging from.
• It indicates the successful working of products over a certain time.
• The operational and environmental conditions under which the product will be working are specified before.

Reliability engineering deals with and implements all the possible ways to achieve maximum reliability at a lesser cost. But it is practically impossible as the companies need to compromise on either. The product can fail in multiple failure modes practically, but while manufacturing the equipment should be manufactured for 100% reliability. Reliability improvement is a continuous process. A vast amount of data collection and data analysis is required to find out the various modes of failure. Various ways also need to be identified to tackle those failures. The various methods used for improving the reliability of equipment are using thicker material, stronger material, simple and standardized materials, and so on. The use of thicker and stronger materials is highly uneconomical and hence, not preferred, whereas using standardized materials provides more reliability.

The reliability of any equipment is measured in the terms of Mean Time To Failure (MTTF) and Mean Time Before Failure (MTBF). The term MTTF is used for the components that failed, cannot be repaired, and need to be replaced. The term MTBF is used for repairable components.

System Reliability

A system is made of several components and equipment. The reliability of the system needs to be calculated by taking into consideration all the components. The reliability of a system can be calculated based on the type of arrangement of the components. The components can be arranged in series or parallel.

For the system with components in series, the reliability is calculated as-

R_s = r_x x r_y x r_z

The image below shows the components of a system arranged in series.

where, r_x, r_y, and r_z are the reliabilities of the components x, y, and z respectively and R_s is the reliability of the system having components in series.

For the system with components in parallel, the reliability is calculated as-

R_p = 1 - [ (1 - r_x) . (1 - r_y) . (1 - r_z) ]

Where, r_x, r_y, and r_z are the reliabilities of the components x, y, and z respectively and R_p is the reliability of the system having components in parallel.

Context and Applications

Maintenance and reliability are used daily in various firms, industries, and companies. The concept is used in almost all industries as the industries are dependent on machinery. The Introduction to maintenance and reliability is useful for the candidates undergoing the courses such as Bachelors of Business Administration, Master in Business Administration, and Master in Operations Management.

Practice Problems

1. Which of the following is the term used for the process of keeping the equipment and system in proper working condition?

1. Reliability
2. Maintenance
3. Safety
4. Coordinate financing

Answer: b

Explanation: Maintenance is the term used for the process of keeping the equipment and system in proper working condition.

2. Which of the following is the term used for denoting the probability that the machine or system will work properly?

1. Reliability
2. Organizational coordination
3. Asset Management
4. Maintenance tasks

Answer: a

Explanation: Reliability is the term used for denoting the probability that the machine or system will work properly.

3. Which of the following is not an element of maintenance?

1. Design decisions
2. Maintainance policies
3. Technician requirement
4. Production process

Answer: d

Explanation: The production process is not an element of maintenance.

4. Which of the following is the term used to measure the reliability of any equipment?

1. MTBF
2. CMRP
3. CMRT
4. FMEA

Answer: a

Explanation: MTBF is the term used to measure the reliability of any equipment.

5. Which of the following is the term used for measuring the reliability of the components that failed, cannot be repaired, and needs to replace?

1. MTTF
2. APICS
3. FMECA
4. SMRP

Answer: a

Explanation: MTTF is the term used for measuring the reliability of the components that failed, cannot be repaired, and needs to replace.